High efficiency flat plate solar energy system

ABSTRACT

A method of making a flat plate solar energy system includes steps of: providing a first metal sheet and a second metal sheet; stamping the first metal sheet to create channels; and fabricating a solar panel by joining the first metal sheet to the second metal sheet such that the channels form passageways between the two sheets. The passageways contain the flow of a working fluid that absorbs and transports heat by phase change. The method further includes steps of creating ports to allow the working fluid to enter and exit the solar panel; and providing a heat exchanger piped to the ports of the solar panel. Optional steps include attaching photovoltaic cells to the solar panel; extracting electricity from the photovoltaic cells; and providing a water storage tank.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 61/668,533, filed 6 Jul. 2012, which is hereby incorporated by reference herein

TECHNICAL FIELD

In the field of solar energy conversion, a method of making a solar energy system made of two metal sheets, one flat and one stamped, that are joined together to convert the majority of solar energy collected by it into electricity and heat. This results in a system that is efficient, low cost, and easy to manufacture.

BACKGROUND ART

Solar collectors for the majority of the today's flat panel solar water heating systems use metal sheets (or fins) coated with solar absorption layer bonded on copper tubes. Water typically runs through the copper tubes to carry the heat away.

For a simple passive system, the water circulation is not closed and flows by natural convection, which is not efficient, and is subject to freezing and scale accumulation, especially when hard water is used.

For more advanced active systems with close-loop circulation, water or water with antifreeze is forced to circulate, usually by electrical pump, between the solar collector and a heat exchanger usually inside of a water storage tank to solve freezing and scaling problems.

SUMMARY OF INVENTION

A method of making a flat plate solar energy system includes steps of: providing a first metal sheet and a second metal sheet; stamping the first metal sheet to create channels; and fabricating a solar panel by joining the first metal sheet to the second metal sheet such that the channels form passageways between the two sheets. The passageways contain the flow of a working fluid that absorbs and transports heat by phase change. The method further includes steps of creating ports to allow the working fluid to enter and exit the solar panel; and providing a heat exchanger piped to the ports of the solar panel, the heat exchanger capable of removing heat from the working fluid. Optional steps include coating the second metal sheet with solar thermal energy absorption layer; attaching photovoltaic cells to the solar panel; extracting electricity from the photovoltaic cells; and providing a water storage tank.

The passageways serve as a loop heat pipe and form an evaporation tube inside the solar panel that directs flow of the working fluid and allows the working fluid to evaporate inside the solar panel from a liquid phase; a vapor tube inside of the solar panel that contains and directs the flow of a vapor comprising a gas phase of the working fluid; and a liquid tube inside of the solar panel that contains and directs the flow of a liquid comprising the liquid phase of the working fluid. The method may include steps of: installing an exit port on the solar panel connected to the vapor tube; affixing an inflow port connected to the liquid tube; piping the heat exchanger to the exit port such that the gas phase of the working fluid can flow out of the solar panel into the heat exchanger; and piping the heat exchanger to the inflow port so that the liquid phase of the working fluid can flow out of the heat exchanger and into the solar panel.

There are 3 preferred embodiments: The first using bubble pumping action is similar to a pulsating heat pipe; a second using a bubble pump with multiple paths to evaporating tube; and a third having a liquid pipe on top of the solar panel so that no pump action is needed.

The step of making channels comprises organizing the channels to form the passageways that result in: making a pumping tube that enables bubble pump action to wet the evaporation tube near the top end; connecting the pumping tube with a lateral tube leading to the evaporation tube; and forming the evaporation tube with a larger diameter than the pumping tube.

Technical Problem

Existing solar energy systems typically employ tubes with fins to promote heat transfer. For example, the fins can be aluminum or copper, and the tubes usually are made of copper because if its good thermal conductivity and compatibility with water. However, copper is expensive. To save on manufacturing cost, some venders use aluminum fins. However due to differences in thermal expansion when using dissimilar metals and because solar collectors are subjected to large swings in operating temperature, there can be significant stresses experienced at the junction of the aluminum fins and copper tubes. This often is the cause of failure in the collector.

Another problem with today's systems is that it is often necessary to find costs savings to be competitive and the fins are usually made very thin. As a result, thermal conductivity suffers and this affects the efficiency of the unit. It also is the reason for significant temperature variations on the surface of the fins.

Another problem with today's systems is that bonding between the fins and the copper tubing creates a barrier to heat transfer in the path from a solar absorbing layer to the coolant, usually water, inside of the copper tubes. This is sometimes addressed by metallurgicaly bonding them together.

Another problem with today's systems is that water circulation is not an efficient way of transferring heat. If the coolant is electrically pumped, this increases operating costs due to the use of electricity, it increases system complexity, initial capital investment and continuing maintenance costs for the system.

Solution to Problem

The solution is a solar collector whose core is an integrated solar absorption panel, or simply a solar panel, made of all or mostly aluminum, which completely avoids the use fins and copper tubes.

This solar panel is made of two aluminum sheets and, preferably, four tubes for ports. A first sheet is stamped with a pattern of ridges or channels. A second sheet is preferably flat. These two sheets are preferably joined together with a pressing machine applying heat and/or pressure to form the solar panel with a one side having the pattern of ridges or channels and the other side being flat. The ridges or channels form passageways between the sheets controlling flow of the working fluid, i.e. typically water and water vapor in most cases. Also, joining the two sheets may be accomplished using welding, brazing, riveting, and gluing.

This solar panel preferably moves the working fluid by “loop heat pipe” principle. The “loop heat pipe” principle is, based on phase transition of the working fluid: the liquid phase of the working fluid is vaporized inside of the solar panel as it absorbs the heat, the vaporized working fluid moves at high speed through the vapor tube to a heat exchanger inside of a water storage tank. At the heat exchanger, the vaporized working fluid is condensed into liquid, which releases the latent heat of vaporization. The liquid is then piped back to the solar panel to complete the cycle.

Advantageous Effects of Invention

Since a solar panel made accordingly is composed of sheet metal, preferably aluminum, with ridges or channels, it is light yet rigid.

The solar water heating system made with the solar panel as described herein has a low manufacturing cost due to significantly reduced material costs and its inherent suitability to automated manufacturing processes. It is also possible to increase the number of channels or “heat transport routes” or the size of them without any significant cost increase.

The solar water heating system made with the solar panel as described herein has a low operating cost because electricity is not required for a fluent circulation pump.

The solar water heating system made with the solar panel as described herein has a higher efficiency than existing systems because there are no fins or tubes needed and so there is no heat barrier between fins and tubes.

The solar energy system made with the solar panel as described herein has design flexibility because the number, pattern, and size of channels or “heat transport routes” may be easily changed according to application requirements. Such change may be implemented with minimal added cost.

The solar energy system made with the solar panel is much more advantageous than simple water circulation because the amount of the heat extracted by phase change is much larger than just raising the temperature. For example, it takes 539 calories of heat to vaporize one gram of water, compared to only 1 calorie of heat to raise 1 gram of water by one degree centigrade.

The solar energy system made with the solar panel is more efficient because water vapor moves much faster than liquid water. Thus, the heat transfer rate is much higher.

In preferred embodiments, the solar energy system made with the solar panel is less expensive because heat transfer is not accomplished using pumps and no outside power is needed for its operation.

BRIEF DESCRIPTION OF DRAWINGS

The drawings illustrate preferred embodiments of the method of the invention and the reference numbers in the drawings are used consistently throughout. New reference numbers in FIG. 2 are given the 200 series numbers. Similarly, new reference numbers in each succeeding drawing are given a corresponding series number beginning with the figure number.

FIG. 1 is an exploded perspective view of the two metal sheets forming a preferred solar panel.

FIG. 2 is a perspective view of a system employing solar absorptions panels.

FIG. 3 is an elevation view showing passageways between the two metal sheets in a first embodiment.

FIG. 4 is an elevation view showing passageways between the two metal sheets in a second embodiment.

FIG. 5 is an elevation view showing passageways between the two metal sheets in a third embodiment.

FIG. 6 is a chart of the steps that may be performed in the method of manufacturing the system.

FIG. 7 is a chart of additional steps that may be performed in the method of manufacturing the system.

FIG. 8 is a chart of additional limitations on the steps that may be performed in the method of manufacturing the system.

DESCRIPTION OF EMBODIMENTS

In the following description, reference is made to the accompanying drawings, which form a part hereof and which illustrate several embodiments of the present invention. The drawings and the preferred embodiments of the invention are presented with the understanding that the present invention is susceptible of embodiments in many different forms and, therefore, other embodiments may be utilized and structural, and operational changes may be made, without departing from the scope of the present invention. For example, the steps in the method of the invention may be performed in any order that results making or using the high efficiency flat plate solar energy system described herein.

FIG. 1 is an exploded perspective view of the two metal sheets forming a preferred solar panel (100) that is part of the flat plate solar energy system (200). The solar panel (100) is also referred to as a solar absorption panel.

FIG. 6 and FIG. 7 chart a method (600) of making the flat plate solar energy 15 system (200). The method (600) may include a first providing step (605), a stamping step (610), a fabricating step (615), a creating step (620), a second providing step (625), a coating step (630), an attaching step (635), a third providing step (640), a passageway limitation (705), an installing step (710), an affixing step (715), a first piping step (720), a second piping step (725), a first channel limitation (805), and a third channel limitation (815).

The first providing step (605) is providing a first metal sheet (105) and a second metal sheet (110). These are the metal sheets that make up the solar panel (100) and they start out as two similar flat plate sheets, preferably of a thermal conducting metal, such as aluminum and copper. Other metals, including alloys, may be used. In other embodiments non-metal materials capable of absorbing heat may be used for the sheets. This includes such materials as plastic.

The stamping step (610) is stamping the first metal sheet (105) to create channels (115). Channels (115) are used to describe the impressions made, but they might equally be described as ridges from the perspective of the other side of the stamped sheet. Thus, as show in FIG. 1, a solar panel (100) preferably consists of two aluminum sheets of at least 4 tubes for ports, with one sheet stamped with pattern for channels (115) for routing the working fluid (335) and the other preferably flat.

These two sheets are preferably joined together with a pressing machine applying heat and/or pressure. Also, the joining of the two sheets may include welding, brazing, riveting, and gluing. In any case, once the two sheets are joined, they form an integrated piece. Once the first metal sheet (105) is joined to the second metal sheet, the combined sheets make tubes or pipes from the channels (115).

The fabricating step (615) is fabricating a solar panel by joining the first metal sheet (105) to the second metal sheet (110) such that the channels (115) form the passageways (405) between the first metal sheet (105) and the second metal sheet (110).

The passageways (405) are within the dotted box enclosure in FIG. 4. The passageways (405) are capable of containing and routing the flow of a working fluid (335) between the first metal sheet (105) and the second metal sheet (110). The working fluid (335), preferably water or water with anti-freeze, is used for, and capable of, absorbing and transporting heat by phase change, which means that the flat plate solar energy system (200) essentially uses the loop heat pipe principle. This is a principle described by two-phase heat transfer. It uses evaporation of the working fluid (335) from its liquid phase to remove heat from the solar panel (100) and passively move it to a condenser, which in the flat plate solar energy system (200) is a heat exchanger (305), which is preferably inside the water storage tank (205). Powered pump operation moving the working fluid may be utilized in other embodiments.

Thus, the preferred transport mechanism for the working fluid (335) is by “loop heat pipe” principle, i.e., based on phase transition of the working fluid: it is vaporized inside of the solar panel (100) as it absorbs the heat; the vapor moves at high speed through the vapor tube (315) to the heat exchanger (305) inside of water storage tank (205). At the heat exchanger (305), the vapor is condensed into liquid which releases the heat. The liquid phase of the working fluid (335) flows back to solar panel (100) via the liquid tube (415) to complete the cycle. This configuration is much more advantageous than water circulation in three fold: (A) The amount of the heat by phase change is much larger than just raising the temperature. For example, it takes 539 calories of heat to vaporize one gram of water, compared to only 1 calorie of heat to raise 1 gram of water by 1 degree Centigrade. (B) Vapor moves much faster than liquid. Thus, heat transfer speed is much faster. And, (C) Heat transfer is accomplished without outside power input.

The loop heat pipe principle is implemented using pattern designs of channels (115). There are an infinite number of compliant designs and several are shown in FIGS. 3-5. With different design patterns, various types of mechanism can by introduced and realized easily.

Compared to a gravity heat pipe, the loop heat pipe principle is known to have an advantage by eliminating the count flow of the liquid state of the working fluid (335). Also, another advantage is that the amount of heat transported is significantly increased and occurs over much longer distance.

However, an operating problem can occur using the loop heat pipe principle. Because there is no counter flow, the top end (140) of the solar panel (100) may not be immersed in the liquid phase of the working fluid (335) and so will not cause the desired phase transition in the working fluid from liquid to vapor. This will result in diminished heat absorption, which in turn can cause overheating of the solar panel (100). To solve this operating problem, preferred embodiments use a channel design providing bubble pump action, which lifts the liquid using vapor bubbles. This solves the problem and wets the upper part of solar panel (100) with liquid working fluid.

Thus, preferred design principles for solar panel include:

(A) It should lift the liquid state working fluid from its normal level up to or near the top of solar panel (100) to promote phase transition over about all of the solar panel (100), not just at lower parts, by bubble pump action, or other means.

(B) The pump action should start at relative low temperature, about 40 degrees Centigrade (40° C.) and at low heat input.

(C) The vapor phase of the working fluid (335) should be able to travel relatively freely above the liquid level within an evaporation tube (325) and within a header tube (310) near the top end (140), which is connected to the vapor tube (315). The header tube (310) is designated as the tube inside the dotted box shown in FIG. 3 and is within the solar panel (100).

(D) There should be lateral channels for working fluid to move around in order to make the temperature more evenly distributed in the horizontal direction. The lateral channels also improve the mechanical rigidity of the solar panel (100). These horizontal connecting passageways are shown in FIG. 1 and designated as the lateral tube (410) in FIG. 4.

By using the loop heat pipe function in preferred embodiments, the temperature of the solar panel (100) and the water in the water storage tank (205) reaches equilibrium quickly. This translates to a lower operating temperature for the solar panel (100). Thus, there is less heat loss at the solar panel (100), since heat loss is very sensitive to the temperature. For example, the radiation heat loss is proportional to the fourth power of temperature or to the cube of the temperature difference between the solar panel and the environment. Thermal conductance and convection losses are more or less proportional to the above mentioned temperature difference.

The creating step (620) is creating ports (125) to allow the working fluid (335) to enter and exit the solar panel (100).

The second providing step (625) is providing a heat exchanger (305) piped to the ports (125) of the solar panel. The heat exchanger (305) is capable of removing heat from the working fluid (335).

The coating step (630) is coating the second metal sheet (110) with solar thermal energy absorption layer (220). The solar thermal energy absorption layer (220) is a coating that promotes conversion of the incident solar radiation to heat. The solar panel (100) is coated preferably on the flat side, which is the side that will face the sun when in service. The coating increases solar heat absorption and may be any number of available options such as black paint, black anodizing, black chrome plating, titanium oxynitride thin film (TiNxOy), etc.

The attaching step (635) is attaching photovoltaic cells (225) to the second metal sheet (110) on the solar panel; and extracting electricity from the photovoltaic cells (225). The photovoltaic cells (225) are preferably placed over the solar thermal energy absorption layer (220), but may be used instead of the solar thermal energy absorption layer (220). The photovoltaic cells (225) will reduce the thermal absorption but their solar to electricity conversion efficiency is only about 18%, so there is sufficient thermal energy even with the photovoltaic cells (225).

Addition of the photovoltaic cells (225) makes it possible for the flat plate solar energy system (200) to produce both hot water and electricity, becoming a hybrid solar system. Since there are common materials and components that may be shared, such as glass glazing, aluminum frame, etc., the cost saving attributable to such combination is real. Compared to a standard photovoltaic module, whose wholesale spot price is about $0.72 per peak electric Watt, it is estimated that the cost extra of the hybrid solar panel system is only about $0.10 or less per peak electric Watt for large deployment. If the electricity produced by the photovoltaic cells (225) is consumed or purchased with Power Purchase Agreement, then the hot water can be considered as a byproduct and will be almost free.

The third providing step (640) is providing a water storage tank (205) having a water-tight chamber to confine the heat exchanger (305) within.

The passageway limitation (705) states that the passageways (405) are further capable of serving as a loop heat pipe. It further requires the passageways (405) to form an evaporation tube (325) inside the solar panel (100) that directs flow of a working fluid (335) and allows the working fluid (335) to evaporate inside the solar panel from liquid phase. It further requires the passageways (405) to form a vapor tube (315) inside of solar panel that contains and directs the flow of a vapor comprising a gas phase of the working fluid (335). It further requires the passageways (405) to form a liquid tube (415) inside of solar panel that contains and directs the flow of a liquid comprising a liquid phase of the working fluid (335).

The installing step (710) is installing an exit port (130) on the solar panel (100) connected to the vapor tube (315).

The affixing step (715) is affixing an inflow port connected to the liquid tube.

The first piping step (720) is piping the heat exchanger to the exit port (130) such that the gas phase of the working fluid (335) can flow out of the solar panel (100) into the heat exchanger (305).

The second piping step (725) is piping the heat exchanger to the inflow port (135) so that the liquid phase of the working fluid (335) can flow out of the heat exchanger (305) and into the solar panel (100).

The first channel limitation (805) is explained with reference to FIG. 4. The first channel limitation (805) is wherein the solar panel (100) comprises a top end (140) and a bottom end (145), the top end (140) intended to be at a higher elevation than the bottom end (145) when placed in service; and wherein the step of wherein the step of making channels comprises organizing the channels to form the passageways that result in: making a pumping tube (330) that enables bubble pump action to wet the evaporation tube (325) near the top end (140); connecting the pumping tube (330) with a lateral tube (410) leading to the evaporation tube (325); and forming the evaporation tube (325) with a larger diameter than the pumping tube (330).

The second channel limitation (810) is explained with reference to FIG. 5. The second channel limitation (810) is wherein the solar panel (100) comprises a top end (140) and a bottom end (145), the top end (140) intended to be at a higher elevation than the bottom end (145) when placed in service; wherein the step of stamping the first metal sheet to create channels (115) comprises organizing the channels (115) to form the passageways (405) that result in: locating the vapor tube near the top end; locating a first liquid tube near the top end; locating a second liquid tube near the bottom end; piping the first liquid tube to the heat exchanger so that liquid flows from the heat exchanger to the first liquid tube; and piping the vapor tube to the heat exchanger and collecting the vapor as the working fluid flows through the evaporation tube toward the bottom end.

The third channel limitation (815) is explained with reference to FIG. 3. The third channel limitation (815) specifies that the solar panel (100) comprises a top end (140) and a bottom end (145). The top end (140) is intended to be at a higher elevation than the bottom end (145) when placed in service. For this third channel limitation (815), the step of stamping the first metal sheet to create channels, the stamping step (610), comprises organizing the channels (115) to form the passageways (405) that result in: locating the vapor tube (315) near the top end (140); locating the liquid tube (415) near the bottom end (145); making a pumping tube (330) that enables bubble pump action to move the working fluid in liquid phase from near the bottom end (145) up towards the top end (140) so that evaporation occurs near the top end (140); forming the evaporation tube (325) with a larger diameter than the pumping tube (330); and making the pumping tube (330) route the working fluid (335) from the liquid tube (415) near the bottom end (145) to a point below the vapor tube (315) near the top end (140) and then turns the working fluid (335) back to flow toward the bottom end (145) where the working fluid (335) connects to the evaporation tube (325).

FIGS. 3-5 illustrate differing design patterns for the channels (115) in an elevation view showing the resulting passageways (405) between the two metal sheets of the solar panel (100). For simplicity only one unit is shown in each figure, but the solar panel (100) may have any combination of channel designs.

FIG. 3 shows bubble pumping action in the pumping tube (330). This action is similar to what might be found in a pulsating heat pipe.

FIG. 4 shows bubble pumping action where the mostly liquid phase (320) of the working fluid (335) has multiple paths leading to the evaporation tube (325). Vapor bubbles are seen rising from the bottom end (145). The arrows within the passageways (405) in this figure and generally in the other figures indicate flow of the working fluid (335).

FIG. 5 shows the liquid tube (415) at the top end (140) of solar panel (100). This design results in a liquid down-flow from the top end (140) into the evaporation tube (325) where no external pumping action is needed.

To enable the channel design of FIG. 3, it is important to maintain control of the diameter of the channel to promote the formation of liquid plugs and vapor slugs within the channels (115). The preferred formula for determining the diameter is the same formula used for a pulsating heat pipe:

$D_{PHP} = {2\sqrt{\frac{\sigma}{g\left( {\rho_{lig} - \rho_{vap}} \right)}}}$

If the diameter of the pumping tube (330) is less than D_(PHP), then the flow of the working fluid (335) is termed “slug flow,” and the bubble rise velocity becomes zero, whether or not this is in working condition. In such a case, the pumping tube (330) is functioning as a pulsate pump. This state would partially satisfy the above noted design principles (A), (B), and (C), but not (D).

For the embodiment shown in FIG. 4, the pumping tube (330) acts as a bubble pump, and its critical diameter follows:

$D_{BP} = {19\sqrt{\frac{\sigma}{g\left( {\rho_{lig} - \rho_{vap}} \right)}}}$

If the diameter of the pumping tube is less than D_(BP), but more than D_(PHP), then bubble pump action will start when there is sufficient heat input and the temperature of the working fluid (335) is high enough. This design pattern satisfies the above noted design principles (A), (C), and (D), but not (B), for it requires a certain temperature and heat input to start functioning.

For the embodiment shown in FIG. 5, the liquid tube (415) is near the top end (140) of the solar panel (100) and in lower passageways (510). The dotted line box surrounds the lower passageways (510), each of which is the liquid tube (415). The working fluid (335) in liquid phase is routed through the vapor tube (315) at a crossover (505). The crossover (505) seals off the liquid tubes from the vapor tube (315) to prevent the flooding of vapor tube (315). A liquid tube (415) at the bottom end (145) is connected to inflow ports that pipe together other solar panels in the system so that working fluid (335) in liquid phase has a more or less similar liquid level in all the solar panels. With this configuration, no pumping action is needed, and the bubble pump effect is reduced or eliminated.

In order for the solar panel (100) to start pumping action even at low heat input and low temperature, a capillary wick may be placed on part of evaporating tube to pump the liquid up by capillary action, while not blocking any lateral tube (410) flow path. Capillary pumping capability may be limited due to its small feature size, which is usually about 30 micrometers. However, it may be sufficient for low heat and low temperature applications. The preferred working fluid (335) in the temperature range of solar water heating system is water. Water is non-toxic, inexpensive, chemically stable, and its thermal transfer performance is about twice as good as other material in this temperature range.

The above-described embodiments including the drawings are examples of the invention and merely provide illustrations of the invention. Other embodiments will be obvious to those skilled in the art. Thus, the scope of the invention is determined by the appended claims and their legal equivalents rather than by the examples given.

INDUSTRIAL APPLICABILITY

The invention has application to the solar energy industry. 

What is claimed is:
 1. A method of making a flat plate solar energy system, the method comprising the steps of: providing a first metal sheet and a second metal sheet; stamping the first metal sheet to create channels; fabricating a solar panel by joining the first metal sheet to the second metal sheet such that the channels form passageways between the first metal sheet and the second metal sheet, said passageways capable of containing flow of a working fluid between the first metal sheet and the second metal sheet, said working fluid capable of absorbing and transporting heat by phase change; creating ports to allow the working fluid to enter and exit the solar panel; and providing a heat exchanger piped to the ports of the solar panel, the heat exchanger capable of removing heat from the working fluid.
 2. The method of claim 1, further comprising the step of coating the second metal sheet with solar thermal energy absorption layer.
 3. The method of claim 1, further comprising the step of attaching photovoltaic cells to the second metal sheet on the solar panel; and extracting electricity from the photovoltaic cells.
 4. The method of claim 1, further comprising the step of providing a water storage tank having a water-tight chamber to confine the heat exchanger within.
 5. The method of claim 1, wherein the passageways are further capable of serving as a loop heat pipe, the passageways forming: an evaporation tube inside the solar panel that directs flow of the working fluid and allows the working fluid to evaporate inside the solar panel from a liquid phase; a vapor tube inside of solar panel that contains and directs the flow of a vapor comprising a gas phase of the working fluid; and a liquid tube inside of solar panel that contains and directs the flow of a liquid comprising the liquid phase of the working fluid; and further comprising the steps of: installing an exit port on the solar panel connected to the vapor tube; affixing an inflow port connected to the liquid tube; piping the heat exchanger to the exit port such that the gas phase of the working fluid can flow out of the solar panel into the heat exchanger; and piping the heat exchanger to the inflow port so that the liquid phase of the working fluid can flow out of the heat exchanger and into the solar panel.
 6. The method of claim 5, wherein the solar panel comprises a top end and a bottom end, the top end intended to be at a higher elevation than the bottom end when placed in service; wherein the step of stamping the first metal sheet to create channels comprises organizing the channels to form the passageways that result in: locating the vapor tube near the top end; locating a first liquid tube near the top end; locating a second liquid tube near the bottom end; piping the first liquid tube to the heat exchanger so that liquid flows from the heat exchanger to the first liquid tube; and piping the vapor tube to the heat exchanger and collecting the vapor as the working fluid flows through the evaporation tube toward the bottom end.
 7. The method of claim 5, wherein the solar panel comprises a top end and a bottom end, the top end intended to be at a higher elevation than the bottom end when placed in service; and wherein the step of making channels comprises organizing the channels to form the passageways that result in: making a pumping tube that enables bubble pump action to wet the evaporation tube near the top end; connecting the pumping tube with a lateral tube leading to the evaporation tube; and forming the evaporation tube with a larger diameter than the pumping tube.
 8. The method of claim 5, wherein the solar panel comprises a top end and a bottom end, the top end intended to be at a higher elevation than the bottom end when placed in service; and wherein the step of stamping the first metal sheet to create channels comprises organizing the channels to form the passageways that result in: locating the vapor tube near the top end; locating the liquid tube near the bottom end; making a pumping tube that enables bubble pump action to move the liquid so that there is evaporation near the top end; forming the evaporation tube with a larger diameter than the pumping tube; and making the pumping tube route the working fluid from the liquid tube near the bottom end to a point below the vapor tube near the top end and then turns the working fluid back to flow toward the bottom end where the working fluid connects to the evaporation tube. 